mysql按日期時間選擇一列中的所有唯一行，另一列中的所有最大行

Question

我需要為每個table_id獲取最新的（按date_time） unique player_id

表：

buyin_id   player_id   table_id       date_time
---------|-----------|----------|--------------------|
    1    |    10     |    21    | 2015-01-26 00:00:01
    2    |    11     |    21    | 2015-01-26 00:00:02
    3    |    12     |    21    | 2015-01-26 00:00:03
    4    |    10     |    21    | 2015-01-26 00:00:04
    5    |    11     |    21    | 2015-01-26 00:00:05
    6    |    12     |    22    | 2015-01-26 00:00:06
    7    |    13     |    22    | 2015-01-26 00:00:07
    8    |    13     |    22    | 2015-01-26 00:00:08

所需結果：

buyin_id   player_id   table_id       date_time
---------|-----------|----------|--------------------|
    3    |    12     |    21    | 2015-01-26 00:00:03
    4    |    10     |    21    | 2015-01-26 00:00:04
    5    |    11     |    21    | 2015-01-26 00:00:05
    6    |    12     |    22    | 2015-01-26 00:00:06
    8    |    13     |    22    | 2015-01-26 00:00:08

我嘗試過這樣的事情，每個table_id只返回1行而不是1行

SELECT pb.buyin_id, pb.player_id, pb.buyin, pb.cashout, pb.cashout_error, pb.date_time
FROM poker_buyin AS pb
INNER JOIN (SELECT player_id, MAX(date_time) AS MaxDateTime
FROM poker_buyin GROUP BY player_id) groupedpb 
ON pb.player_id = groupedpb.player_id 
AND pb.date_time = groupedpb.MaxDateTime
WHERE pb.player_id = '$player_id'";

Answer 1

您提到的查詢將查找每個玩家ID的最新記錄。 然后，您對其進行過濾以找到一名球員，那么您將獲得一行。

如果要查找每個球員和桌子的最新記錄，則內部查詢需要這樣：

            SELECT  MAX(buyin_id) buyin_id
              FROM  poker_buyin
             GROUP  BY player_id, table_id

這將從表中獲取代表最新播放器/表組合的行ID。

然后使用它從表中提取記錄，例如（ http://sqlfiddle.com/#!2/be68b7/2/0 ）

SELECT whatever_columns
  FROM poker_buyin
 WHERE buyin_id IN
       (
            SELECT  MAX(buyin_id) buyin_id
              FROM  poker_buyin
             GROUP  BY player_id, table_id
       )
 WHERE player_id = '$player_id'
 ORDER BY player_id, table_id

該查詢中有一個小技巧：buyin_id值不斷上升，因此這是為每個組合選擇最新記錄的好方法。

Answer 2

如果在結果列中不需要buyin_id ，則很簡單：

SELECT DISTINCT player_id, table_id, max(date_time) as dt 
FROM `poker_buyin ` 
GROUP BY player_id, table_id